#' partykit's Party Rules to data.table
#'
#' Get the rules of a party model to be used in a data.table.
#' 
#' @param x Your party model.
#' @param i Ignore this unless you give names to rules
#' @param ... Other parameters to pass to the rule generator. Ignoring this is preferred.
#' 
#' @return The rules in a character frame.
#' 
#' @export

GetPartyRules <- function(x, i = NULL, ...) {
  if (is.null(i)) i <- nodeids(x, terminal = TRUE)
  if (length(i) > 1) {
    ret <- sapply(i, GetPartyRules, x = x)
    names(ret) <- if (is.character(i)) i else names(x)[i]
    return(ret)
  }
  if (is.character(i) && !is.null(names(x)))
    i <- which(names(x) %in% i)
  stopifnot(length(i) == 1 & is.numeric(i))
  stopifnot(i <= length(x) & i >= 1)
  i <- as.integer(i)
  dat <- data_party(x, i)  
  if (!is.null(x$fitted)) {
    findx <- which("(fitted)" == names(dat))[1]  
    fit <- dat[,findx:ncol(dat), drop = FALSE]   
    dat <- dat[,-(findx:ncol(dat)), drop = FALSE]
    if (ncol(dat) == 0)
      dat <- x$data
  } else {
    fit <- NULL  
    dat <- x$data
  }
  
  rule <- c()
  
  recFun <- function(node) {
    if (id_node(node) == i) return(NULL)   
    kid <- sapply(kids_node(node), id_node)
    whichkid <- max(which(kid <= i))
    split <- split_node(node)
    ivar <- varid_split(split)
    svar <- names(dat)[ivar]
    index <- index_split(split)
    if (is.factor(dat[, svar])) {
      if (is.null(index)) 
        index <- ((1:nlevels(dat[, svar])) > breaks_split(split)) + 1
      slevels <- levels(dat[, svar])[index == whichkid]
      srule <- paste(svar, " %in% c(\"", 
                     paste(slevels, collapse = "\", \"", sep = ""), "\")",
                     sep = "")
    } else {
      if (is.null(index)) index <- 1:length(kid)
      breaks <- cbind(c(-Inf, breaks_split(split)), 
                      c(breaks_split(split), Inf))
      sbreak <- breaks[index == whichkid,]
      right <- right_split(split)
      srule <- c()
      if (is.finite(sbreak[1]))
        srule <- c(srule, 
                   paste(svar, ifelse(right, ">", ">="), sbreak[1]))
      if (is.finite(sbreak[2]))
        srule <- c(srule, 
                   paste(svar, ifelse(right, "<=", "<"), sbreak[2]))
      srule <- paste(srule, collapse = " & ")
    }
    rule <<- c(rule, srule)
    return(recFun(node[[whichkid]]))
  }
  node <- recFun(node_party(x))
  paste(rule, collapse = " & ")
}